This invention relates to a holder device for holding a semiconductor, such as a wafer, or a conductor, and more particularly to a holder device for holding a semiconductor wafer or the like by an electrostatic attractive force in vacuum orin a reduced-pressure atmosphere. The invention also relates to a semiconductor producing apparatus having such a holder device.
A device for holding a semiconductor wafer by an electrostatic attractive force is described, for example, in Japanese Patent Unexamined Publication No. 63-95644 and Applied Mechanical Engineering (the May, 1989 issue, pages 129 to 131). In these prior art techniques, an insulating film is formed at least on a surface of an electrode, and this insulating film is formed by mixing a conductor, a semiconductor, or a low-resistivity material with an insulating material of a high volume resistivity.
Recently, with a microscopic design of a circuit pattern of semiconductor chips, there have been a demand for a holder device capable of holding a wafer in a more flat manner for heating and cooling the wafer during a production process in vacuum or a reduced-pressure atmosphere, and also there has been a demand for a handling device which is clean and is capable of holding a reverse surface of the wafer.
The holding force obtainable with the devices of the above prior art techniques is small. Further, even if voltage of opposite sign (polarity) is applied in order to remove residual static charges in the insulating film when releasing the wafer from the holder device, this operation requires 3 to 5 seconds. Further, since the thin insulating film is formed on the electrode, the insulating film is liable to be damaged by a thermal stress due to a change in the ambient temperature, and also the insulating film is liable to be damaged or short-circuited upon contact of other object with the surface of the insulating film.
Further, because of the nature of the structure, the electrode of a high rigidity for supporting the thin insulating film, as well as a device frame for supporting this electrode, has been needed. Therefore, it has been difficult to achieve a compact construction of the device.
Further, because of an electric field generated around the wafer and the holder device subjected to high voltage, dust around them is attracted toward the device, and deposits on the wafer, thereby contaminating the wafer.